I agree with aussieump and Diligent. By the time you're at a yellow card, if it's not manifestly obvious what the card is for, you haven't been communicating as well as you could have been up to that point. I usually don't bring the player over to me whatsoever. Half the time, they're already walking towards the bench as they know. At the most, I'll say, "Sorry, off you go, please" (in a neutral tone of voice) and (try to) direct with an open upwards-facing palm to the technical bench. Then I'll pull out the card, and show my colleague the duration if necessary. Diligent's correct - green cards are good times to try to communicate. That's what the warning is for - to deter future behaviour. Once you're at a yellow you're not deterring - you're penalizing.